Conventionally, silver paste has been used to bond a semiconductor chip to a lead frame or an electrode member in the step of producing a semiconductor device. The treatment for the sticking is conducted by coating a paste-form adhesive on a die pad of a lead frame, or the like, mounting a semiconductor chip on the die pad, and then setting the paste-form adhesive layer.
However, about the paste-form adhesive, the amount of the coated adhesive, the shape of the coated adhesive, and on the like are largely varied in accordance with the viscosity behavior thereof, a deterioration thereof, and on the like. As a result, the thickness of the formed paste-form adhesive layer becomes uneven so that the reliability in strength of bonding a semiconductor chip is poor. In other words, if the amount of the paste-form adhesive coated on an electrode member is insufficient, the bonding strength between the electrode member and a semiconductor chip becomes low so that in a subsequent wire bonding step, the semiconductor chip is peeled. On the other hand, if the amount of the coated paste-form adhesive is too large, this adhesive flows out to stretch over the semiconductor chip so that the characteristic becomes poor. Thus, the yield or the reliability lowers. Such problems about the adhesion treatment become particularly remarkable with an increase in the size of semiconductor chips. It is therefore necessary to control the amount of the coated paste-form adhesive frequently. Thus, the workability or the productivity is deteriorated.
In this coating step of a paste-form adhesive, there is a method of coating the adhesive onto a lead frame or a forming chip by an independent operation. In this method, however, it is difficult to make the paste-form adhesive layer even. Moreover, an especial machine or a longtime is required to coat the paste-form adhesive. Thus, a dicing film which makes a semiconductor wafer to be bonded and held in a dicing step and further gives an adhesive layer, for bonding a chip, which is necessary for a mounting step is disclosed (refer to Patent Document 1, for example).
This dicing film has a structure wherein a adhesive layer and an adhesive layer are successively laminated on a supporting substrate. That is, a semiconductor wafer is diced in the state that the wafer is held on the adhesive layer, and then the supporting substrate is extended; the chipped works are peeled together with the adhesive layer; the peeled works are individually collected; and further the chipped works are bonded onto an adherend such as a lead frame through the adhesive layer.
When a dicing die bond film including a dicing film and a die bond film laminated thereon is used and a semiconductor wafer is diced while being held by the die bond film, it is necessary to cut the die bond film and the semiconductor wafer at the same time. However, in a general dicing method using a diamond blade, it is necessary to reduce the cutting speed and costs are increased because there are potential problems such as adhesion of the die bond film with the dicing film due to heat that is generated during dicing, sticking of semiconductor chips due to generation of cutting scraps, and attachment of cutting scraps onto the side of the semiconductor chips.
In recent years, a method of forming grooves on the surface of a semiconductor wafer and then performing backside grinding to obtain an individual semiconductor chip (refer to Patent Document 2, for example, also referred to as “a DBG (Dicing Before Grinding) method”) and a method of forming a modified region by irradiating a line to be divided on the semiconductor wafer with a laser beam to make the division of the semiconductor wafer easy at the line to be divided and then applying a tensile force to break the semiconductor wafer and obtain an individual semiconductor chip (refer to Patent Documents 3 and 4, for example, also referred to as “Stealth Dicing (a registered trademark)”) have been proposed. According to these methods, the occurrence of poor operations such as chipping can be decreased especially in the case where the semiconductor wafer is thin, and the kerf width is made to be narrower than the conventional kerf width to improve the yield of the semiconductor chip.
It is necessary to break the die bond film by applying a tensile force to obtain individual semiconductor chips with a die bond film by the above-described method while the semiconductor wafer is being held by the die bond film.
In Patent Document 5, an adhesive sheet is disclosed which is used in the DBG method and the Stealth Dicing method and in which the breaking strength at 25° C. is 0.1 MPa or more and 10 MPa or less and the breaking elongation rate is 1% or more and 40% or less. However, because the breaking elongation rate of the adhesive sheet of Patent Document 5 is 40% or less, it may break before the semiconductor wafer breaks when the tensile force is applied in the Stealth Dicing method, and the semiconductor wafer may be divided at a line that is different from the line to be divided.
In Patent Document 6, a dicing tape is disclosed that is used in the Stealth Dicing method and in which the tensile load at 10% of the tape elongation rate is 15 N or more. However, in the case where the yield point elongation of the dicing tape of Patent Document 6 itself is small, the dicing tape undergoes plastic deformation or breaks in the expansion step, and therefore, a normal dicing may not be performed.
Further, in Patent Document 7, a dicing tape integrated adhesive sheet is disclosed that is used in the DBG method and the Stealth Dicing method and having a dicing tape in which the yield point is not shown in tensile deformation and an adhesive sheet in which the break elongation exceeds 40% and 400% or less. However, in the case where the break elongation of the dicing tape of the dicing tape integrated adhesive sheet of Patent Document 7 is too small, the adhesive sheet may firstly break in the expansion step.